Method of assembling aircraft structures



Oct. 14,1947. 4 M. WATTER, 2,429,144

METHOD OF ASSEMBLING AIRCRAFT STRUCTURES Original Filed March 26, 1941 4 Sheets-Sheet l willw" il r. in

7 INVENTOR Mwhael Watier ATTORNEY Oct. 14, 1947. M. WATTER METHOD OF ASSEMBLING AIRCRAFT STRUCTURES Original Filed March 26, 1941 4 Sheets-Sheet. 2

I N VEN TOR A TTORNE Y Michael WaZZer Oct. 14, 1947.

MQWATTER METHOD OF ASSEMBLING AIRCRAFTSTRUCTURES Original Filed March 26, 1941 4 Sheets-Sheet 3 JNVENTOR whaeZ Waiier ATTORNEY &

Oct. 14, '1947. M, WATTER 2,429,144

METHOD Of ASSEMBLING AIRCRAFT STRUCTURES Original Filed March 26, l941- 4 Sheets-Sheet 4 INVE NTOk M c/76162 waiter BY PM ATTQRNEY Patented Oct. 14, 1947 3 UNIT ED STAT ES PATENT F F-I'C E METHOD OF ASSEMBLIQNG AIRCRAFT STRUCTURES Michael Waiter, Philadelphia, Pa, assig'nor to The Budd Company, Philadelphia, Pa., acorporation of Pennsylvania 'OrigFnaI application iMarch 26, 1941, Serial 'No.

385,235. Divided and this application September 14, 1942, Serial No. 458,249

This invention relates to methodsof constructing or assembling airfoil structures for airplanes, and is divided from a pending application Serial No. 385,235, filed March 26, 1941, now Patent No. 2,396,625, and relating to aircraft structures.

jHeretofore, it has been the practice to assemble airfoil structures by starting with the usual spar structure and building the remaining frame parts on to the same, and finally adding to the frame assembly the skin structure. Such a method of assembling airfoil structures does not lend itself particularly well to airfoil structures which are made up by Welding and inasmuch as the 'number of welds "required is great and in that the majorityof these Welds would have to take place among the frame parts and in locations substantially inaccessible to a welding tool.

:It is, therefore, the object of the present invention to provide a method-oi-assembling or constructing an airfoil structure wherein minimum welding operations for efiecting the final assembly-of the airfoil structure may be had, and had with the least possible interference for the welding tool.

It is also the object of the present invention to provide amethod of assembly wherein the majority of the welding operations may take place at the time of making up the subassemblies, and one where the .more delicate welding operations may .be done .on :these sub-assemblies and free of interfering frame structure.

According to the present invention, the leading edge, skin blankets, ribs, spar and trailing edge structures are preformed and'provided'with attaching portions for connection with one another. The leadingedge, one of the skin blankets, and the ribsare the firstassembled together, then the other skin blanket is connected to the ribs, access being provided through the space adjacent to the ribs, and between therearward edges of the skin blanket. By omitting the spar in this main part of the assembly, access is readily had for the welding of the skin blanket to "the ribs.

Finally, the spar and the trailing edge structure is welded to the ribs already located in their proper position in the thus far assembled structure, The

welding operations for connecting these sub-assemblies together are few and relatively easy to make. i

For a better understanding of the invention, reference may be :had to the fOlloWingdBtEtilGd description taken in connection with the accompanying drawing in which,

Figure l is an enlarged sectional view of the forward part of the airioil structure, including Claims. (Cl. 29-148.2)

2 the ieading edge thereof and taken 0f the portion -l-"l of Figure '4;

Figure 2 is an enlarged sectional view of the airfoil structure-at the union'of the trailing edge and spar structures with the rib and rearward edges-of theskin "blankets and takeno'f the portionL-Z of Fieure 4;

Figure 3 is 'anexploded view of fihG-fifil'fOllStI-llfiture showing the sub-assemblies thereof;

Figure 4 is a view in section of the airfoil with all the sub-assemblies finallyconnected together;

=Figur'es'5, 6, land -8 are "views illustrating the steps in the method of assembly of the'parts of the airfoil structure and just prior to the adding of the tra'iling edge structure;

Figure '9 is an enlarged -'fragmentar-y View, in section, and taken along the line 9-9 of Figure 2, looking in the direction of the arrows thereof and showing' the union'dfthe web portion of the rib, the spar, and the trailingedge;

Figure 1 0 is -'a similar view but "taken along the line l0-Hlof l ligure 2 and looking in the direction of the arrows thereof and showing the union of the web cap strip, the spar, and the trailing edge; and

Figure 11 is a fragmentary *view in elevation andloo'king at the rearward face of the spar.

Referring now to Figs. '3 'and ljthere are shown the various sub-assemblies of the airfoilstruc'ture to which thepresent method of assembling is applied. These structures include -a leading edge H", top and bottom skin blankets l2 and H, a rib structure iii, a spar structure l4 and a final trailing edge structure [5. 'These sub-assemblies, when connected together, make up a final airfoil structure 16, shown in Fig. 4. All of these subassemblies are preformed in the various jigs made special for their pecu'liar shapes, and all of the same are provided Withcertain portions to which attachment is made of other of the sub-assemlolies. On referring now to Figs. 1 and '2, showing an enlarged view of these structures and with the following description, these attaching portions will 'become more apparent.

Asshown in Fig. l, the "leading edge structure I includes a nose piece H over which a skin i8 is stretched. 'Tliis nose piece H includes inner and outer angle'members l9 and 20. The outer angle member Ell has 'a laterally extending flange portion "2| to which the skin blanket I 8 is welded. It will beunderstoocl that for a-single leading edge structure there will be provided throughout the length of thesame a series of'n'ose pieces I! over which the entire skin of the leading edge section is stretched. Disposed between the nose channel elements 4|.

having an opening 23 therein through Which' controls, incidental to the operation of the aircraft, may pass.

The skin I8 of the top of the nose pieces I! extends beyond the rearward end thereof for overlapping connection with the skin blanket; assembly I2. In order to provide on the leading edge at this location an attaching portion to which the skin blanket I2 may be attached, there is extended spanwise of the same a metal piece 24 of Z-shape cross-section and having spaced flanges 25 and 26, and an intermediate web 21 to the latter of which the actual weld for the seccuring of the skin blanket is made, as indicated at 28. The skin I8 and the flange 25 are weldingly secured to the flange 2| of the outer angle member 20 of the nose piece II, in the manner as indicated at 29.

In order to steady the spanwise extending attaching piece 24 of the leading edge at a location removed from its connection with the skin I8 and at the same time to provide means to which the rib structure I3 may be readily attached, there is weldingly secured, as indicated at 30, an attaching piece 3| having a laterally extendin flange 32 which is connected flush to the piece 24 by the same union 28 that. the skin blanket is attached to the piece 24. As seen at the bottom of Fig. 1, there is another attaching piece, similar to the piece 3|, connected with the leading edge section. This other one is indicated at 33 and is welded at 34 to the nose piece II.

On the lower end of the leading edge structure, is a spanwise extending attaching portion 35 connected to a flange 36 of the attaching piece 33 and also to the skin I8 and flange 2| of the outer angle member 26 as indicated at 31. Provided at this location, is a spanwise extending reinforcing element 38 welded to the piece 35 and in turn secured along with the rearward edge of the skin I8 to the lower skin blanket I2, the union being indicated at 39.

The upper skin blanket I2 includes a skin 43 extended over and secured to a plurality of channel-shaped reinforcing elements 4| having inwardly extending-portions 42 and 43 adapted for connection with similar vertical portions of other In making this connection of the portions 42 and 43 of respective channel pieces 4 I, there is disposed between the inwardly extending portions a tubular stringer 44 having flattened radially extending connecting portions 45 adapted to be disposed between the inwardly extending portions of the channels and weldingly secured thereto making combined union of the inwardly extending portions 42 and 43 and the stringer 44. The channel element 4| on the forward edge of the skin blanket assembly I2 overlaps the skin 46 and its portion 42 is adapted for attachment to the spanwise attaching piece 24 of the leading edge assembly II. In its final location the top skin blanket I2 will have its skin 43 overlap with the skin I8 of the leading edge II,- and a welded union as indicated at 46 is finally made.

Adapted to partially surround the stringer 44 and connected to the union of the stringer with the vertical-portions 42 and 43 of the channel elements, are attaching clips 41 which serve for the connection of the blanket assembly to the rib I3. These attaching clips are connected to the skin blanket and form a part of the skin blanket sub-assembly. They have an attaching portion 48 by which they are welded to the channel elements 4|. The lower skin blanket assembly I2 is constructed similarly to the upper skin blanket I2 and a further detail description of it is believed to be unnecessary. The union of the lower skin blanket I2 to the leading edge structure II is made as indicated by the weld at 39. An additional attaching clip 49, however, is provided in this lower blanket assembly. It is carried by a vertically extending portion 43 of the forward channel element 4|. The attaching clips 48 also form a part of the lower skin blanket assembly.

Coming now to the rib structure I3, it will be seen from Figs. 1 and 2 that there are provided generally upper and lower cap strips 58 and 5| retained in spaced relation by a web plate 52 cor rugated as indicated at 53 and having cut-out openings 54. These cap strips and 5|, respectively, have stiffening flanges 55 and 56 extending in opposite directions and the section through the cap strip generally taking the form of a Z. The forward ends of the cap strips 50 and 5| are formed to receive respectively the attaching pieces 3| and 33 of the leading edge II, so that when the ribs are assembled to the leadin edge II, so that when the ribs are assembled to the leading edge structure there can be made readily therewith the welds 55' and 56' respectively. At the same time, the welds 51 and 58 are made of the attaching clips 41 and 48 respectively of the skin blanket assemblies I2 and I 2. These welds 51 and 53 are made readily to the cap strips 50 and 5| respectively by disposing the welding tongs respectively in the spaces at opposite sides of the rib.

The spar structure I4 is a complete assembly and has therein openings 60 spaced across the s same, corresponding to the spacing of the ribs which are adapted for attachment with the spar structure or assembly I4. This spar assembly includes Z-shaped cap strips BI and 62 to which is welded a. corrugated web portion 63, having flanges 64 and 64' forming the side wall of an opening 60. The cap strips 56 and 5| of the ribs I3 at their trailing ends are relieved of portions of their flanges 55 and 56 and in exchange for this loss of metal, are provided with reinforcing pieces 65 and 66, respectively. These pieces are welded respectively as indicated at 6! and 68 to the cap strips. When the spar I4 is in its final position the rearward ends of the cap strips 58 and 5| having the reinforcing elements 65 and 66, respectively, enter the opening 60 along with the web 52 and intoface-to-face alignment with the side wall 64-see Fig. 10. The rearward edges of the skin 40 forming a part of the skin blanket assemblies II and II' overlap the cap strips 6| and 62 of the spar structure I4 and extended over these rearward edges of the skin 40 to reinforce the same are reinforcing skin plates 69 and 69.

The trailing edge structure I5 includes the cap strips I0 and II and truss elements I2 and I3. The rearward ends of its cap strips I0 and II are held in spaced relation by a plate I4, see Fig. 3. The forward end of the trailing edge has a strut member I5 as shown in Figs. 9 and 10, which is of such dimension as to fit within the opening 6|] of the spar structure. The connections of the strut member I5 with the forwardends of the 'cap strips '10 and *H of the trailing edge structure is made by means of gusset plates #6 also adapted to fit within the opening 60 of the spar structure. The trailing edge structure consists of a frame over which is spread in the final assembly of the entire airfoil structure a skin 'ILeither of metal or of fabric, the connection of the same with the trailing edge frame being made in the usual manner and adapted to overlap the reinforcing strips 69 and '69 on the rearward edges of the skin blankets i2 and I2.

With the trailing edge fitted with its'strut mem- -ber in the opening 60 and with the spar structure in its proper location over the rearward endsof the ribs so that they are projected into the openings 60, a simple welding operation can be made, and the airfoil be given its final iorm. This welding union takes place along the side wall faces Stand 64', as indicated at 80 and 80'. It should be particularly apparent now that the spar structure and trailing edge are'the last assemblies to be attached and that this is done after the ribs have been definitely located between the skin blankets and-connected to the leading edge structure,

Referring now particularly to Figs. 5, 6, '7 and 8, the steps in the general assembly, up to the connecting of the spar structure, will be more clearly brought out and the advantages of this method of assembly of facilitating the welding operations will become more apparent. As shown in Fig. 5, the top skin blanket t2 is'first attached to the leading edge structure H. While this attachment is being made, the skin blanket is retained by clamping elements 8! and 82. Welding tool tongs 83 operate on opposite sides of the blanket'and the union at 46 is made. Since the lower skin blanket l2 and the ribs 13 have not been assembled up to this time, the unions 28 of the flange 32 of the leading edge and of the spanwise extending attaching portion 24 may be readily made with the inwardly extending portion 4-2 of the channel piece H to complete the union of the skin blanket I2 with the leading edge ll.

The next step in the method is as shown in Fig. 6, to add the rib assemblies l3. Since the lower skin blank l2 has not been added up to this time, ready access is had for the welding tongs by straddling the individual rib for attachment of the clips 4'! to the cap strip 50 and the attachment of the rib with the leading edge attaching piece 3|. With the ribs finally secured to the top skin blanket l2, the lower skin blanket I2 is then added to form the assemblage shown in Fig. 7. The welding tongs for the welding of the lower skin blanket with the leading edge structure I l to provide the welded union 39 can be made by the welding tongs straddling the lower blanket with one of the tongs inside of the space defined by the skin blankets. With the welding tongs removed and both arranged to enter the spaces between the rearward edges of the skin blankets and on opposite sides of the ribs the Welded union 56 0f the cap strip 5| with the attaching piece 33 of the leading edge structure and the welded unions 58 of the attaching clips 48 to the cap strip 59 is now readily made. It will be apparent that up to this time the spar structure serving to close the assembly has not been added, whereby the method has afforded simple welding operations in the making up of the bulk of the airfoil.

Coming now to the step in the method of adding the spar structure as shown in Fig. 8 and 6 the "closing of the assembly, it will :be seen "that as explained above, the sparstru'ctureis put in placeso that its openings .60 register with. the projection of the ribs 13. At this time the trailing structure can be added and a final welding toperation for the securing of the spam structure and the trailing edge structure to the rib now takes place. This is done after the welding of the cap strips BI :and 62 of the .sparstructure i4 is made with the rearward edges of the skin blanket 40 of the skin blanket assemblies f2 and I2 and -oi the reinforcing strips 65 thereto, as indicated at 81.

It should now be apparent from the method 1 of'assemblingianiairfoil structure just defined that there has been provided a method which may be easily carried out and wherein the welding operations can be performedwith minimum of interference for'the welding tools.

While various changes may be suggested as to the detailed steps in the method of time'forming the airfoil, it shall be understood that'these steps are meant to be included :by .the present invention as defined by theappended claims- What is claimed is:

1. The method of manufacturing an: airfoil structure which consistsin prefabricating as unitary sub-assembly structures aleading edgeJstru'cture, top and bottom skin blankets, rib :structures, and a spar structure and then, in consecutive order, finally securing the leading edge: ofone'of said blankets toan edge of said leading edge structure, disposing said rib structures in position and finally securing them to said leading edge-structureand to said one blanket finally securing the other blanket to the other edge of said leading edge structure and to said rib structures, with access for and Working in partgor wholly inside the assembly, and then finally placing and securing said spar structure to said rib structures and skin blankets to close the interior space, and working outside the assembly.

2. The method of assembling an airfoil structure which consists in prefabricating leading edge, rib, and top and bottom skin blanket subassemblies, and then, in succession, finally securing one of the skin blanket sub-assemblies to the leading edge sub-assembly, finally securing the rib sub-assembly to the leadin edge subassembly and to the skin blanket sub-assembly, and then finally securing the other of the skin blanket sub-assemblies to the leading edge sub assembly and to the rib sub-assembly, with access for and working in part or wholly inside the assembly.

3. The method of assembling an airfoil structure of closed construction comprising, as separate sub-assemblies, a leading edge section, a pair of top and bottom skin blankets, a single main spar having an opening therethrough with a side wall attaching portion extending in a plane transverse to the plane of the spar and aligned with the small dimension of the spar, and a rib having a projection adapted to extend into said, opening for face-to-face engagement with the side wall attaching portion of the spar so that the spar can be secured by a shear connection to the rib Which is accessible for connection from a location external of the construction, the steps of which consist of first positioning together the leading edge section, skin blankets, and the rib, and finally securing them together, with access for and working in part or. wholly inside the assembly, then positioning the spar so that the rib projection is disposed in its opening and aligned with the side wall attaching portion, and finally securing the rib projection and the side wall attaching portion together, A Working from a. location outside the fully enclosed assem-' bly structure.

4. The method of assembling an airfoil structure of closed construction comprising, as separate sub-assemblies, a leading edge section, a pair of top and bottom skin blankets, a single main spar having an opening therethrough with a side wall attaching portion extending in a plane transverse to the plane of the spar and aligned with the small dimension of the spar, a rib having a projection adapted to extend into said opening for face-to-face engagement with the side wall attaching portion of the spar so that the spar can be secured by a' shear connection to the rib, which connection is accessible from a location external of the construction, and a. trailing edge frame having a projection adapted to fit within the opening into overlapping relation with the side wall attaching portion of the spar, the steps of which consist of first positioning together the leading edge section, skin blankets and rib and finally securing them together, with access for and working in part or wholly inside the assembly, positioning the spar so that the rib projection is disposed in its opening and aligned with the side wall attaching portion, positioning the trailing edge frame so that its projection is aligned with the opening of the spar and in overlapping relation with the side wall attaching portion and with the rib projection,

- and finally securing the spar and the trailing edge frame to the rib projection, Working from a location outside the fully enclosed assembly structure.

5. The method of assembling an airfoil of the portions of the skin blankets and leading edge, 8

working partly inside and partly outside the assembly, securing the ribs to the leading edge, working inside the assembly, securing the attaching clips of the skin blankets to the ribs through an overlapping engagement substantially in the plane of the ribs, working inside the assembly, and finally securing the spar to the ribs, working outside the assembly.

MICHAEL WATTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,856,143 'I'haden May 3, 1932 1,388,543 Barling Aug, 23, 1921 1,802,721 Junkers Apr. 28, 1931 2,019,272 Ragsdale Oct. 29, 1935 1,902,956 Hughes Mar. 28, 1933 1,781,723 Fox Nov. 18, 1930 1,784,501 Staiger Dec. 9, 1930 2,087,626 Minshal1 July 20, 1937 2,275,038 Whitesell, Jr., et a1. Mar. 3, 1942 

